Development of pre-grouted prestressing stand with moisture reactive epoxy resin

摘要

For use in bridge and building construction, Sumitomo Electric markets pre-grouted prestressing strand that is composed of prestressing steel coated with liquid epoxy resin and covered with a corrugated polyethylene sheath. As the epoxy resin is a liquid state at the time of construction, a pre-grouted prestressing strand can be tensioned in the same way as the unbonded strand system. In one or two years, the epoxy resin hardens at normal temperature, providing anti-corrosion properties to the pregrouted prestressing strand, creating complete bond between the strand and the concrete. Existing pre-grouted prestressing strand has a weakness such as unexpected heat reaction which may result in hardening of the epoxy resin before tensioning in a situation of high temperature due to excessive hydration reaction of the massive concrete. Therefore it cannot be applied to the main cable (longitudinal tendon) that penetrates the massive concrete section of highway bridge girders. The authors have developed a new pre-grouted prestressing strand with moisture reactive epoxy resin that has a low temperature sensitivity to hardening, which can be applied to the construction that has a massive concrete section. Laboratory tests and practical tests have been conduced on the new pregrouted prestressing strand and the authors confirmed that its tensioning limit is a month at the highest temperature situation and it hardens in two years even at the lowest temperature situation. The newly developed pre-grouted prestressing strand is now available for use in main cables.